a) Field of the Invention:
The present invention relates to a light weight mineral foam composition and to a process for preparing the same.
b) Brief Description of the Prior Art:
To the Applicant's knowledge, there are presently three main processes for preparing mineral foams.
The first one of these processes is commonly known as process for preparing "chemical" foams. This process consists in generating gaseous bubbles by a chemical reaction into a mixture. This process is used in particular for preparing cellular concretes like those sold under the trademarks SIPOREX.RTM. and YTONG.RTM. by Internationalla Siporex AB, of Stockholm, Sweden. The composition which is used for preparing this concrete generally consists of a mixture of water, hydraulic cement of the Portland type, and fine granular material such as natural silica sand, to which is added a substance generating gas during mixing. Such a substance generating gas can be aluminum powder which, in the presence of the lime (CaOH).sub.2 contained in the concrete, reacts to form a calcium aluminate of formula CaO.Al.sub.2 O.sub.3, and gaseous hydrogen which is generated within the composition and transforms the same into a foam. The product that is so obtained is subjected to curing until the concrete is set and then to a treatment with saturated vapour in an autoclave. The final product has a density ranging from 25 to 30 lb/pi.sup.3.
The second process known to the Applicant is commonly known as process for preparing "mechanical" foams. This process consists in mixing or mechanically stirring a suspension of the basic components of the foam in water, in the presence of a foaming agent. This process which is used in particular for the production of gypsum panel like those sold under the trademark GYPROC.RTM. consists in molding between two sheets of cardboards a mineral foam obtained by mechanical stirring of a mixture of water, gypsum and a suitable foaming agent. There are many other applications of this process for preparing "mechanical" foams. By way of example, reference can be made to British patent No. 1,381,289 which discloses a process for preparing a magnesium concrete foam. Reference can also be made to U.S. Pat. No. 3,661,603 which discloses a process for preparing a foam of asbestos fibers with a cementitious material.
The third process known to the Applicant for the preparation of mineral foams, consists in forming a foam, adding this foam to a suspension of other components in water, and homogenizing the resulting mixture. An example of known products prepared by this process are the structural and non structural concretes sold under the trademark MEARLCRETE.RTM. by Mearl Corporation of New Jersey. The process used by this company consists in mixing a foam obtained from a solution of proteins with a mortar or a concrete made from hydraulic cement in order to obtain, depending on the amount of foam that is added, different products that are classified in three different groups according to the densities, the first group containing the product of a density ranging from 16 to 27 lb/pi.sup.3 the second group those of a density ranging from 27 to 50 lb/pi.sup.3 and the third group those of a density ranging from 50 to 120 lb/pi.sup.3.
The light weight mineral foams that are prepared according to the three above-mentioned processes and have a density ranging from 10 to 40 lb/pi.sup.3 are useful in particular for thermo-insulation under ambient temperature conditions, acoustic absorption and refractory insulation at high temperature. Obviously, in the latter case, the selection of the substances used to form of the foam and of the kind of binders that hold the same together, is essential.